Artificial tooth.



F'. W. MMDONALD..

ARTIFICIAL TOOTH.

narran sTATns- PATENT ernten.

FREDERICK W. MACDONALD, OF DETROIT, MICHIGAN.

ARTIFICIAL TOOTH. i

Specication of Letters Patent.v

Patented nay e, race .1

Application filed November 10, `1906. Serial No. 342,886.

To all whom it may concern.' i

Be it known that I, FREDERICK W. MAC- DONALD, a citizen of the United States of America, residing at Detroit, in the county of rayne and State of'Michigan, have invented certain new and useful Im rove.

ments in Artificial Teeth, of lwhich te following is a specification, reference being had therein to the accompanying drawings.

The invention relates generally to the con struction of artificial teeth,'and more paru` ticularly to the means of attachmentofa tooth or tooth sectionfto its support, bei peculiarly adapted for use in bridgef an crown work.

It is the object of the invention to provide a strong attachment between the porcelain and metallic portions and one in which vtheprincipal stresses are transmitted' directly from one member tothe other, instead of through the medium of a cement.'

.' invention consists in- Fig. 1; Fig.l 3 is a rear elevation ofthe porce-A lain facing. construction. v

A is the porcelain facin in bridge work, and B is t therefor. C is a member secured tegral with, and backing B, and is a recess in the rear .facing of the porcelain, with which the member C is engaged.

Heretofore the engagement between Athe member C and the porcelain has been ef- Fig. 4 illustrates a modied e metallic backing to or preferably fected in various ways, such, for instance, as

by forminga dove tail 'engagement with an entering slot extending to the end of the porcelain. Or, again, by the formation of; a central recess in the porcelain, in which the engaging metallic member entersf laterally,

`and is securedby cement. Therst of thesey constructions .is objectionable in that `the entering slot weakens theporcelain members, and, further because the parts must be ention ofthetooth,

'tions c and'd orcelain facing 'and of a tooth, as used j rojecting forward from the gaged by sliding the porcelain parallel tothe acking, which is prevented by a slight bending of the latter. The 4second construction is objectionable for the reason that' the stresses .are transmitted through the .me-

- dium of the cement instead of directly from the porcelain to the metal. With my in- Ventron, these difliculties are-avoided by the peculiar formation of the member and recess Dbeingsuch that the Vmembers may be engaged by a' relative angular movement and when engaged are interlocked, and are indirect contaetat points for the transmission'of the principal stresses. vAs specifically illustrated, the recess I) is under cut at its upper and lower ends, as indicated at a and b, .and

at the upper end, which isin the `thiclmr porthe recess is deeper.4 TheA member C .is provided with projecting poror respectively fitting v the un! der cut portions a and t of the recess. Thus, the entering slot, or mouth of 'the recess I) is contracted to be less in diameter than between the points c and d of the member. C, thereby preventing disengagement lby a transverse movement. It 1s however possible to engage or disengage thel member C by an angular'movement for `the reason that -v clearance is provided between the ing portions c and the adjacent'wa ofthe recessMv Thus, by an larly moving the member C, the point may be first withdrawn from, therecess, and when clear 'of the shoulder t, the member C may be drawn downward to disengage tion cgi It will be understood that with theconstructionas described, the member A may be readily engaged or disengaged from the meniber B but that the stresses to which the .tooth is ordinarily subjected have no tendency 'tolpriecte the projecting porcause. disengagement. Thus, in biting, the I stress of the member A is transmitted to the member B through the and d. Again a downward pressure sometimes exerted on the member A'will be trans.-

mitted through the contacting points a and c. Lateral pressure against the outer-face ofthe l member A will be transmitted directly to the member B, and lateral' movement in the opposte direction exerted against "the in-v c ed upper face' of the member A will be transmitted to the member C :through the contacting points 'o 4and c. -In fact the 'only contacting points b.

movement which can causedisengagement, f

l viz., the swinging of the lower end ot the member A outward about the -upper end of the point c as a pivot cannot be caused by pressure against any portion of the exposed surface of the member A. To complete the securing of the members A and B they are cemented to each other, the cement filling the clearance space between the point portion c andthe adjacent Wall of the recess and also the other clearances incident to the construction.' It is not essential that the member C 1,

should closely irit the recess D, for even if a slight clearance'is left all around, which is subsequently iilled with cement, only compression stresses will be transmitted through ythe cement.

I deem it preferable, however, to have the principal stresses transmitted directly from the memberA to the member B.

It is obvious that the porcelain member constructed as described is very .much stronger than Where provided with an entering slot extending to either end. The deepest portion of the recess is inthe thickest portion of .the member and the contraction in size of the entering oriiice produces strong cross connections at both top and bottom. rlhese may be further strengthened by providing a rib or bead c adjacent to the edge of the orii'ice, as illustrated in Fig. l and 3.

In Fig. 4 a modiiied construction is illustrated, in which A^ is the porcelain member of the double tooth, and B the backing therefor. These partsv are formed With interlocking shoulders f and g from which the upward stress on the tooth, in biting, is trans mitted directly to the Ametal backing. At the same time, the members can be interlocked by the engagement of the projecting j .member on the backing with the recess D,

and by an angular movement While, after the l members are thus engaged, the cement is iilled in the clearance space II of the recess D, disenga ement is prevented. c

What I c aim as my invention is:

1. In an'artiiicial tooth, a recessed member and a member having an undercut )rojection for Ainterlockingvwith said recessed member, j andof greater extent than the orifice of said recess, said vmembers being engageable only by a relative angular movement in a plane transverse to their meeting faces.

2. In an artificial tooth, a member having an undercut recess therein With a Acontracted entering oriiice, and a-member having an in tegral projecting portion of greater extent than said orifice and substantially fitting the undercut portion of said recess, said members being engageable only by an angular movement in a plane transverse to their meeting taces.

3. In an arti'licial tooth, a member having an under cut recess, a contacting member, a projection on said contacting member for engaging said under cut recess and a strengthening rib adjacent to the vunder cut portion ol the iirst mentioned member.

In testimony whereof I aH'lX my signature in presence of two Witnesses.

FREDERICK W. MACDONALD.

Witnesses: l

i AMELIA WILLIAMS, JAMES P. BARRY. 

